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view lib/IR/ConstantFold.cpp @ 107:a03ddd01be7e
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| author | Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Sun, 31 Jan 2016 17:34:49 +0900 |
| parents | 7d135dc70f03 |
| children | 1172e4bd9c6f |
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//===- ConstantFold.cpp - LLVM constant folder ----------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements folding of constants for LLVM. This implements the // (internal) ConstantFold.h interface, which is used by the // ConstantExpr::get* methods to automatically fold constants when possible. // // The current constant folding implementation is implemented in two pieces: the // pieces that don't need DataLayout, and the pieces that do. This is to avoid // a dependence in IR on Target. // //===----------------------------------------------------------------------===// #include "ConstantFold.h" #include "llvm/ADT/SmallVector.h" #include "llvm/IR/Constants.h" #include "llvm/IR/DerivedTypes.h" #include "llvm/IR/Function.h" #include "llvm/IR/GetElementPtrTypeIterator.h" #include "llvm/IR/GlobalAlias.h" #include "llvm/IR/GlobalVariable.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/Operator.h" #include "llvm/IR/PatternMatch.h" #include "llvm/Support/Compiler.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/ManagedStatic.h" #include "llvm/Support/MathExtras.h" #include <limits> using namespace llvm; using namespace llvm::PatternMatch; //===----------------------------------------------------------------------===// // ConstantFold*Instruction Implementations //===----------------------------------------------------------------------===// /// BitCastConstantVector - Convert the specified vector Constant node to the /// specified vector type. At this point, we know that the elements of the /// input vector constant are all simple integer or FP values. static Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) { if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); if (CV->isNullValue()) return Constant::getNullValue(DstTy); // If this cast changes element count then we can't handle it here: // doing so requires endianness information. This should be handled by // Analysis/ConstantFolding.cpp unsigned NumElts = DstTy->getNumElements(); if (NumElts != CV->getType()->getVectorNumElements()) return nullptr; Type *DstEltTy = DstTy->getElementType(); SmallVector<Constant*, 16> Result; Type *Ty = IntegerType::get(CV->getContext(), 32); for (unsigned i = 0; i != NumElts; ++i) { Constant *C = ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i)); C = ConstantExpr::getBitCast(C, DstEltTy); Result.push_back(C); } return ConstantVector::get(Result); } /// This function determines which opcode to use to fold two constant cast /// expressions together. It uses CastInst::isEliminableCastPair to determine /// the opcode. Consequently its just a wrapper around that function. /// @brief Determine if it is valid to fold a cast of a cast static unsigned foldConstantCastPair( unsigned opc, ///< opcode of the second cast constant expression ConstantExpr *Op, ///< the first cast constant expression Type *DstTy ///< destination type of the first cast ) { assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); assert(CastInst::isCast(opc) && "Invalid cast opcode"); // The types and opcodes for the two Cast constant expressions Type *SrcTy = Op->getOperand(0)->getType(); Type *MidTy = Op->getType(); Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); Instruction::CastOps secondOp = Instruction::CastOps(opc); // Assume that pointers are never more than 64 bits wide, and only use this // for the middle type. Otherwise we could end up folding away illegal // bitcasts between address spaces with different sizes. IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext()); // Let CastInst::isEliminableCastPair do the heavy lifting. return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, nullptr, FakeIntPtrTy, nullptr); } static Constant *FoldBitCast(Constant *V, Type *DestTy) { Type *SrcTy = V->getType(); if (SrcTy == DestTy) return V; // no-op cast // Check to see if we are casting a pointer to an aggregate to a pointer to // the first element. If so, return the appropriate GEP instruction. if (PointerType *PTy = dyn_cast<PointerType>(V->getType())) if (PointerType *DPTy = dyn_cast<PointerType>(DestTy)) if (PTy->getAddressSpace() == DPTy->getAddressSpace() && PTy->getElementType()->isSized()) { SmallVector<Value*, 8> IdxList; Value *Zero = Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); IdxList.push_back(Zero); Type *ElTy = PTy->getElementType(); while (ElTy != DPTy->getElementType()) { if (StructType *STy = dyn_cast<StructType>(ElTy)) { if (STy->getNumElements() == 0) break; ElTy = STy->getElementType(0); IdxList.push_back(Zero); } else if (SequentialType *STy = dyn_cast<SequentialType>(ElTy)) { if (ElTy->isPointerTy()) break; // Can't index into pointers! ElTy = STy->getElementType(); IdxList.push_back(Zero); } else { break; } } if (ElTy == DPTy->getElementType()) // This GEP is inbounds because all indices are zero. return ConstantExpr::getInBoundsGetElementPtr(PTy->getElementType(), V, IdxList); } // Handle casts from one vector constant to another. We know that the src // and dest type have the same size (otherwise its an illegal cast). if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && "Not cast between same sized vectors!"); SrcTy = nullptr; // First, check for null. Undef is already handled. if (isa<ConstantAggregateZero>(V)) return Constant::getNullValue(DestTy); // Handle ConstantVector and ConstantAggregateVector. return BitCastConstantVector(V, DestPTy); } // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts // This allows for other simplifications (although some of them // can only be handled by Analysis/ConstantFolding.cpp). if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); } // Finally, implement bitcast folding now. The code below doesn't handle // bitcast right. if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. return ConstantPointerNull::get(cast<PointerType>(DestTy)); // Handle integral constant input. if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { if (DestTy->isIntegerTy()) // Integral -> Integral. This is a no-op because the bit widths must // be the same. Consequently, we just fold to V. return V; // See note below regarding the PPC_FP128 restriction. if (DestTy->isFloatingPointTy() && !DestTy->isPPC_FP128Ty()) return ConstantFP::get(DestTy->getContext(), APFloat(DestTy->getFltSemantics(), CI->getValue())); // Otherwise, can't fold this (vector?) return nullptr; } // Handle ConstantFP input: FP -> Integral. if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) { // PPC_FP128 is really the sum of two consecutive doubles, where the first // double is always stored first in memory, regardless of the target // endianness. The memory layout of i128, however, depends on the target // endianness, and so we can't fold this without target endianness // information. This should instead be handled by // Analysis/ConstantFolding.cpp if (FP->getType()->isPPC_FP128Ty()) return nullptr; return ConstantInt::get(FP->getContext(), FP->getValueAPF().bitcastToAPInt()); } return nullptr; } /// ExtractConstantBytes - V is an integer constant which only has a subset of /// its bytes used. The bytes used are indicated by ByteStart (which is the /// first byte used, counting from the least significant byte) and ByteSize, /// which is the number of bytes used. /// /// This function analyzes the specified constant to see if the specified byte /// range can be returned as a simplified constant. If so, the constant is /// returned, otherwise null is returned. /// static Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, unsigned ByteSize) { assert(C->getType()->isIntegerTy() && (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && "Non-byte sized integer input"); unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; assert(ByteSize && "Must be accessing some piece"); assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); assert(ByteSize != CSize && "Should not extract everything"); // Constant Integers are simple. if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { APInt V = CI->getValue(); if (ByteStart) V = V.lshr(ByteStart*8); V = V.trunc(ByteSize*8); return ConstantInt::get(CI->getContext(), V); } // In the input is a constant expr, we might be able to recursively simplify. // If not, we definitely can't do anything. ConstantExpr *CE = dyn_cast<ConstantExpr>(C); if (!CE) return nullptr; switch (CE->getOpcode()) { default: return nullptr; case Instruction::Or: { Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); if (!RHS) return nullptr; // X | -1 -> -1. if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) if (RHSC->isAllOnesValue()) return RHSC; Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); if (!LHS) return nullptr; return ConstantExpr::getOr(LHS, RHS); } case Instruction::And: { Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); if (!RHS) return nullptr; // X & 0 -> 0. if (RHS->isNullValue()) return RHS; Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); if (!LHS) return nullptr; return ConstantExpr::getAnd(LHS, RHS); } case Instruction::LShr: { ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); if (!Amt) return nullptr; unsigned ShAmt = Amt->getZExtValue(); // Cannot analyze non-byte shifts. if ((ShAmt & 7) != 0) return nullptr; ShAmt >>= 3; // If the extract is known to be all zeros, return zero. if (ByteStart >= CSize-ShAmt) return Constant::getNullValue(IntegerType::get(CE->getContext(), ByteSize*8)); // If the extract is known to be fully in the input, extract it. if (ByteStart+ByteSize+ShAmt <= CSize) return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); // TODO: Handle the 'partially zero' case. return nullptr; } case Instruction::Shl: { ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); if (!Amt) return nullptr; unsigned ShAmt = Amt->getZExtValue(); // Cannot analyze non-byte shifts. if ((ShAmt & 7) != 0) return nullptr; ShAmt >>= 3; // If the extract is known to be all zeros, return zero. if (ByteStart+ByteSize <= ShAmt) return Constant::getNullValue(IntegerType::get(CE->getContext(), ByteSize*8)); // If the extract is known to be fully in the input, extract it. if (ByteStart >= ShAmt) return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); // TODO: Handle the 'partially zero' case. return nullptr; } case Instruction::ZExt: { unsigned SrcBitSize = cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); // If extracting something that is completely zero, return 0. if (ByteStart*8 >= SrcBitSize) return Constant::getNullValue(IntegerType::get(CE->getContext(), ByteSize*8)); // If exactly extracting the input, return it. if (ByteStart == 0 && ByteSize*8 == SrcBitSize) return CE->getOperand(0); // If extracting something completely in the input, if if the input is a // multiple of 8 bits, recurse. if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); // Otherwise, if extracting a subset of the input, which is not multiple of // 8 bits, do a shift and trunc to get the bits. if ((ByteStart+ByteSize)*8 < SrcBitSize) { assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); Constant *Res = CE->getOperand(0); if (ByteStart) Res = ConstantExpr::getLShr(Res, ConstantInt::get(Res->getType(), ByteStart*8)); return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), ByteSize*8)); } // TODO: Handle the 'partially zero' case. return nullptr; } } } /// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof /// on Ty, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedSizeOf(Type *Ty, Type *DestTy, bool Folded) { if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (StructType *STy = dyn_cast<StructType>(Ty)) if (!STy->isPacked()) { unsigned NumElems = STy->getNumElements(); // An empty struct has size zero. if (NumElems == 0) return ConstantExpr::getNullValue(DestTy); // Check for a struct with all members having the same size. Constant *MemberSize = getFoldedSizeOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberSize != getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) { Constant *N = ConstantInt::get(DestTy, NumElems); return ConstantExpr::getNUWMul(MemberSize, N); } } // Pointer size doesn't depend on the pointee type, so canonicalize them // to an arbitrary pointee. if (PointerType *PTy = dyn_cast<PointerType>(Ty)) if (!PTy->getElementType()->isIntegerTy(1)) return getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), PTy->getAddressSpace()), DestTy, true); // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return nullptr; // Base case: Get a regular sizeof expression. Constant *C = ConstantExpr::getSizeOf(Ty); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } /// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof /// on Ty, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedAlignOf(Type *Ty, Type *DestTy, bool Folded) { // The alignment of an array is equal to the alignment of the // array element. Note that this is not always true for vectors. if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } if (StructType *STy = dyn_cast<StructType>(Ty)) { // Packed structs always have an alignment of 1. if (STy->isPacked()) return ConstantInt::get(DestTy, 1); // Otherwise, struct alignment is the maximum alignment of any member. // Without target data, we can't compare much, but we can check to see // if all the members have the same alignment. unsigned NumElems = STy->getNumElements(); // An empty struct has minimal alignment. if (NumElems == 0) return ConstantInt::get(DestTy, 1); // Check for a struct with all members having the same alignment. Constant *MemberAlign = getFoldedAlignOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) return MemberAlign; } // Pointer alignment doesn't depend on the pointee type, so canonicalize them // to an arbitrary pointee. if (PointerType *PTy = dyn_cast<PointerType>(Ty)) if (!PTy->getElementType()->isIntegerTy(1)) return getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), PTy->getAddressSpace()), DestTy, true); // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return nullptr; // Base case: Get a regular alignof expression. Constant *C = ConstantExpr::getAlignOf(Ty); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } /// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof /// on Ty and FieldNo, with any known factors factored out. If Folded is false, /// return null if no factoring was possible, to avoid endlessly /// bouncing an unfoldable expression back into the top-level folder. /// static Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo, Type *DestTy, bool Folded) { if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, DestTy, false), FieldNo, DestTy); Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); return ConstantExpr::getNUWMul(E, N); } if (StructType *STy = dyn_cast<StructType>(Ty)) if (!STy->isPacked()) { unsigned NumElems = STy->getNumElements(); // An empty struct has no members. if (NumElems == 0) return nullptr; // Check for a struct with all members having the same size. Constant *MemberSize = getFoldedSizeOf(STy->getElementType(0), DestTy, true); bool AllSame = true; for (unsigned i = 1; i != NumElems; ++i) if (MemberSize != getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { AllSame = false; break; } if (AllSame) { Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, DestTy, false), FieldNo, DestTy); return ConstantExpr::getNUWMul(MemberSize, N); } } // If there's no interesting folding happening, bail so that we don't create // a constant that looks like it needs folding but really doesn't. if (!Folded) return nullptr; // Base case: Get a regular offsetof expression. Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, DestTy, false), C, DestTy); return C; } Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, Type *DestTy) { if (isa<UndefValue>(V)) { // zext(undef) = 0, because the top bits will be zero. // sext(undef) = 0, because the top bits will all be the same. // [us]itofp(undef) = 0, because the result value is bounded. if (opc == Instruction::ZExt || opc == Instruction::SExt || opc == Instruction::UIToFP || opc == Instruction::SIToFP) return Constant::getNullValue(DestTy); return UndefValue::get(DestTy); } if (V->isNullValue() && !DestTy->isX86_MMXTy()) return Constant::getNullValue(DestTy); // If the cast operand is a constant expression, there's a few things we can // do to try to simplify it. if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { if (CE->isCast()) { // Try hard to fold cast of cast because they are often eliminable. if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); } else if (CE->getOpcode() == Instruction::GetElementPtr && // Do not fold addrspacecast (gep 0, .., 0). It might make the // addrspacecast uncanonicalized. opc != Instruction::AddrSpaceCast) { // If all of the indexes in the GEP are null values, there is no pointer // adjustment going on. We might as well cast the source pointer. bool isAllNull = true; for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) if (!CE->getOperand(i)->isNullValue()) { isAllNull = false; break; } if (isAllNull) // This is casting one pointer type to another, always BitCast return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); } } // If the cast operand is a constant vector, perform the cast by // operating on each element. In the cast of bitcasts, the element // count may be mismatched; don't attempt to handle that here. if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && DestTy->isVectorTy() && DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { SmallVector<Constant*, 16> res; VectorType *DestVecTy = cast<VectorType>(DestTy); Type *DstEltTy = DestVecTy->getElementType(); Type *Ty = IntegerType::get(V->getContext(), 32); for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { Constant *C = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); } return ConstantVector::get(res); } // We actually have to do a cast now. Perform the cast according to the // opcode specified. switch (opc) { default: llvm_unreachable("Failed to cast constant expression"); case Instruction::FPTrunc: case Instruction::FPExt: if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { bool ignored; APFloat Val = FPC->getValueAPF(); Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf : DestTy->isFloatTy() ? APFloat::IEEEsingle : DestTy->isDoubleTy() ? APFloat::IEEEdouble : DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : DestTy->isFP128Ty() ? APFloat::IEEEquad : DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble : APFloat::Bogus, APFloat::rmNearestTiesToEven, &ignored); return ConstantFP::get(V->getContext(), Val); } return nullptr; // Can't fold. case Instruction::FPToUI: case Instruction::FPToSI: if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { const APFloat &V = FPC->getValueAPF(); bool ignored; uint64_t x[2]; uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); if (APFloat::opInvalidOp == V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, APFloat::rmTowardZero, &ignored)) { // Undefined behavior invoked - the destination type can't represent // the input constant. return UndefValue::get(DestTy); } APInt Val(DestBitWidth, x); return ConstantInt::get(FPC->getContext(), Val); } return nullptr; // Can't fold. case Instruction::IntToPtr: //always treated as unsigned if (V->isNullValue()) // Is it an integral null value? return ConstantPointerNull::get(cast<PointerType>(DestTy)); return nullptr; // Other pointer types cannot be casted case Instruction::PtrToInt: // always treated as unsigned // Is it a null pointer value? if (V->isNullValue()) return ConstantInt::get(DestTy, 0); // If this is a sizeof-like expression, pull out multiplications by // known factors to expose them to subsequent folding. If it's an // alignof-like expression, factor out known factors. if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) if (CE->getOpcode() == Instruction::GetElementPtr && CE->getOperand(0)->isNullValue()) { GEPOperator *GEPO = cast<GEPOperator>(CE); Type *Ty = GEPO->getSourceElementType(); if (CE->getNumOperands() == 2) { // Handle a sizeof-like expression. Constant *Idx = CE->getOperand(1); bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, DestTy, false), Idx, DestTy); return ConstantExpr::getMul(C, Idx); } } else if (CE->getNumOperands() == 3 && CE->getOperand(1)->isNullValue()) { // Handle an alignof-like expression. if (StructType *STy = dyn_cast<StructType>(Ty)) if (!STy->isPacked()) { ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); if (CI->isOne() && STy->getNumElements() == 2 && STy->getElementType(0)->isIntegerTy(1)) { return getFoldedAlignOf(STy->getElementType(1), DestTy, false); } } // Handle an offsetof-like expression. if (Ty->isStructTy() || Ty->isArrayTy()) { if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), DestTy, false)) return C; } } } // Other pointer types cannot be casted return nullptr; case Instruction::UIToFP: case Instruction::SIToFP: if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { APInt api = CI->getValue(); APFloat apf(DestTy->getFltSemantics(), APInt::getNullValue(DestTy->getPrimitiveSizeInBits())); if (APFloat::opOverflow & apf.convertFromAPInt(api, opc==Instruction::SIToFP, APFloat::rmNearestTiesToEven)) { // Undefined behavior invoked - the destination type can't represent // the input constant. return UndefValue::get(DestTy); } return ConstantFP::get(V->getContext(), apf); } return nullptr; case Instruction::ZExt: if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); return ConstantInt::get(V->getContext(), CI->getValue().zext(BitWidth)); } return nullptr; case Instruction::SExt: if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); return ConstantInt::get(V->getContext(), CI->getValue().sext(BitWidth)); } return nullptr; case Instruction::Trunc: { if (V->getType()->isVectorTy()) return nullptr; uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { return ConstantInt::get(V->getContext(), CI->getValue().trunc(DestBitWidth)); } // The input must be a constantexpr. See if we can simplify this based on // the bytes we are demanding. Only do this if the source and dest are an // even multiple of a byte. if ((DestBitWidth & 7) == 0 && (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) return Res; return nullptr; } case Instruction::BitCast: return FoldBitCast(V, DestTy); case Instruction::AddrSpaceCast: return nullptr; } } Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond, Constant *V1, Constant *V2) { // Check for i1 and vector true/false conditions. if (Cond->isNullValue()) return V2; if (Cond->isAllOnesValue()) return V1; // If the condition is a vector constant, fold the result elementwise. if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { SmallVector<Constant*, 16> Result; Type *Ty = IntegerType::get(CondV->getContext(), 32); for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ Constant *V; Constant *V1Element = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, i)); Constant *V2Element = ConstantExpr::getExtractElement(V2, ConstantInt::get(Ty, i)); Constant *Cond = dyn_cast<Constant>(CondV->getOperand(i)); if (V1Element == V2Element) { V = V1Element; } else if (isa<UndefValue>(Cond)) { V = isa<UndefValue>(V1Element) ? V1Element : V2Element; } else { if (!isa<ConstantInt>(Cond)) break; V = Cond->isNullValue() ? V2Element : V1Element; } Result.push_back(V); } // If we were able to build the vector, return it. if (Result.size() == V1->getType()->getVectorNumElements()) return ConstantVector::get(Result); } if (isa<UndefValue>(Cond)) { if (isa<UndefValue>(V1)) return V1; return V2; } if (isa<UndefValue>(V1)) return V2; if (isa<UndefValue>(V2)) return V1; if (V1 == V2) return V1; if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { if (TrueVal->getOpcode() == Instruction::Select) if (TrueVal->getOperand(0) == Cond) return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); } if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { if (FalseVal->getOpcode() == Instruction::Select) if (FalseVal->getOperand(0) == Cond) return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); } return nullptr; } Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, Constant *Idx) { if (isa<UndefValue>(Val)) // ee(undef, x) -> undef return UndefValue::get(Val->getType()->getVectorElementType()); if (Val->isNullValue()) // ee(zero, x) -> zero return Constant::getNullValue(Val->getType()->getVectorElementType()); // ee({w,x,y,z}, undef) -> undef if (isa<UndefValue>(Idx)) return UndefValue::get(Val->getType()->getVectorElementType()); if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { // ee({w,x,y,z}, wrong_value) -> undef if (CIdx->uge(Val->getType()->getVectorNumElements())) return UndefValue::get(Val->getType()->getVectorElementType()); return Val->getAggregateElement(CIdx->getZExtValue()); } return nullptr; } Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, Constant *Elt, Constant *Idx) { if (isa<UndefValue>(Idx)) return UndefValue::get(Val->getType()); ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); if (!CIdx) return nullptr; unsigned NumElts = Val->getType()->getVectorNumElements(); if (CIdx->uge(NumElts)) return UndefValue::get(Val->getType()); SmallVector<Constant*, 16> Result; Result.reserve(NumElts); auto *Ty = Type::getInt32Ty(Val->getContext()); uint64_t IdxVal = CIdx->getZExtValue(); for (unsigned i = 0; i != NumElts; ++i) { if (i == IdxVal) { Result.push_back(Elt); continue; } Constant *C = ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); Result.push_back(C); } return ConstantVector::get(Result); } Constant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, Constant *V2, Constant *Mask) { unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); Type *EltTy = V1->getType()->getVectorElementType(); // Undefined shuffle mask -> undefined value. if (isa<UndefValue>(Mask)) return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); // Don't break the bitcode reader hack. if (isa<ConstantExpr>(Mask)) return nullptr; unsigned SrcNumElts = V1->getType()->getVectorNumElements(); // Loop over the shuffle mask, evaluating each element. SmallVector<Constant*, 32> Result; for (unsigned i = 0; i != MaskNumElts; ++i) { int Elt = ShuffleVectorInst::getMaskValue(Mask, i); if (Elt == -1) { Result.push_back(UndefValue::get(EltTy)); continue; } Constant *InElt; if (unsigned(Elt) >= SrcNumElts*2) InElt = UndefValue::get(EltTy); else if (unsigned(Elt) >= SrcNumElts) { Type *Ty = IntegerType::get(V2->getContext(), 32); InElt = ConstantExpr::getExtractElement(V2, ConstantInt::get(Ty, Elt - SrcNumElts)); } else { Type *Ty = IntegerType::get(V1->getContext(), 32); InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); } Result.push_back(InElt); } return ConstantVector::get(Result); } Constant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, ArrayRef<unsigned> Idxs) { // Base case: no indices, so return the entire value. if (Idxs.empty()) return Agg; if (Constant *C = Agg->getAggregateElement(Idxs[0])) return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); return nullptr; } Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, Constant *Val, ArrayRef<unsigned> Idxs) { // Base case: no indices, so replace the entire value. if (Idxs.empty()) return Val; unsigned NumElts; if (StructType *ST = dyn_cast<StructType>(Agg->getType())) NumElts = ST->getNumElements(); else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) NumElts = AT->getNumElements(); else NumElts = Agg->getType()->getVectorNumElements(); SmallVector<Constant*, 32> Result; for (unsigned i = 0; i != NumElts; ++i) { Constant *C = Agg->getAggregateElement(i); if (!C) return nullptr; if (Idxs[0] == i) C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); Result.push_back(C); } if (StructType *ST = dyn_cast<StructType>(Agg->getType())) return ConstantStruct::get(ST, Result); if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) return ConstantArray::get(AT, Result); return ConstantVector::get(Result); } Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, Constant *C2) { // Handle UndefValue up front. if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { switch (Opcode) { case Instruction::Xor: if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // Handle undef ^ undef -> 0 special case. This is a common // idiom (misuse). return Constant::getNullValue(C1->getType()); // Fallthrough case Instruction::Add: case Instruction::Sub: return UndefValue::get(C1->getType()); case Instruction::And: if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef return C1; return Constant::getNullValue(C1->getType()); // undef & X -> 0 case Instruction::Mul: { // undef * undef -> undef if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) return C1; const APInt *CV; // X * undef -> undef if X is odd if (match(C1, m_APInt(CV)) || match(C2, m_APInt(CV))) if ((*CV)[0]) return UndefValue::get(C1->getType()); // X * undef -> 0 otherwise return Constant::getNullValue(C1->getType()); } case Instruction::SDiv: case Instruction::UDiv: // X / undef -> undef if (match(C1, m_Zero())) return C2; // undef / 0 -> undef // undef / 1 -> undef if (match(C2, m_Zero()) || match(C2, m_One())) return C1; // undef / X -> 0 otherwise return Constant::getNullValue(C1->getType()); case Instruction::URem: case Instruction::SRem: // X % undef -> undef if (match(C2, m_Undef())) return C2; // undef % 0 -> undef if (match(C2, m_Zero())) return C1; // undef % X -> 0 otherwise return Constant::getNullValue(C1->getType()); case Instruction::Or: // X | undef -> -1 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef return C1; return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 case Instruction::LShr: // X >>l undef -> undef if (isa<UndefValue>(C2)) return C2; // undef >>l 0 -> undef if (match(C2, m_Zero())) return C1; // undef >>l X -> 0 return Constant::getNullValue(C1->getType()); case Instruction::AShr: // X >>a undef -> undef if (isa<UndefValue>(C2)) return C2; // undef >>a 0 -> undef if (match(C2, m_Zero())) return C1; // TODO: undef >>a X -> undef if the shift is exact // undef >>a X -> 0 return Constant::getNullValue(C1->getType()); case Instruction::Shl: // X << undef -> undef if (isa<UndefValue>(C2)) return C2; // undef << 0 -> undef if (match(C2, m_Zero())) return C1; // undef << X -> 0 return Constant::getNullValue(C1->getType()); } } // Handle simplifications when the RHS is a constant int. if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { switch (Opcode) { case Instruction::Add: if (CI2->equalsInt(0)) return C1; // X + 0 == X break; case Instruction::Sub: if (CI2->equalsInt(0)) return C1; // X - 0 == X break; case Instruction::Mul: if (CI2->equalsInt(0)) return C2; // X * 0 == 0 if (CI2->equalsInt(1)) return C1; // X * 1 == X break; case Instruction::UDiv: case Instruction::SDiv: if (CI2->equalsInt(1)) return C1; // X / 1 == X if (CI2->equalsInt(0)) return UndefValue::get(CI2->getType()); // X / 0 == undef break; case Instruction::URem: case Instruction::SRem: if (CI2->equalsInt(1)) return Constant::getNullValue(CI2->getType()); // X % 1 == 0 if (CI2->equalsInt(0)) return UndefValue::get(CI2->getType()); // X % 0 == undef break; case Instruction::And: if (CI2->isZero()) return C2; // X & 0 == 0 if (CI2->isAllOnesValue()) return C1; // X & -1 == X if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) if (CE1->getOpcode() == Instruction::ZExt) { unsigned DstWidth = CI2->getType()->getBitWidth(); unsigned SrcWidth = CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) return C1; } // If and'ing the address of a global with a constant, fold it. if (CE1->getOpcode() == Instruction::PtrToInt && isa<GlobalValue>(CE1->getOperand(0))) { GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); // Functions are at least 4-byte aligned. unsigned GVAlign = GV->getAlignment(); if (isa<Function>(GV)) GVAlign = std::max(GVAlign, 4U); if (GVAlign > 1) { unsigned DstWidth = CI2->getType()->getBitWidth(); unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); // If checking bits we know are clear, return zero. if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) return Constant::getNullValue(CI2->getType()); } } } break; case Instruction::Or: if (CI2->equalsInt(0)) return C1; // X | 0 == X if (CI2->isAllOnesValue()) return C2; // X | -1 == -1 break; case Instruction::Xor: if (CI2->equalsInt(0)) return C1; // X ^ 0 == X if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { switch (CE1->getOpcode()) { default: break; case Instruction::ICmp: case Instruction::FCmp: // cmp pred ^ true -> cmp !pred assert(CI2->equalsInt(1)); CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); pred = CmpInst::getInversePredicate(pred); return ConstantExpr::getCompare(pred, CE1->getOperand(0), CE1->getOperand(1)); } } break; case Instruction::AShr: // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. return ConstantExpr::getLShr(C1, C2); break; } } else if (isa<ConstantInt>(C1)) { // If C1 is a ConstantInt and C2 is not, swap the operands. if (Instruction::isCommutative(Opcode)) return ConstantExpr::get(Opcode, C2, C1); } // At this point we know neither constant is an UndefValue. if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { const APInt &C1V = CI1->getValue(); const APInt &C2V = CI2->getValue(); switch (Opcode) { default: break; case Instruction::Add: return ConstantInt::get(CI1->getContext(), C1V + C2V); case Instruction::Sub: return ConstantInt::get(CI1->getContext(), C1V - C2V); case Instruction::Mul: return ConstantInt::get(CI1->getContext(), C1V * C2V); case Instruction::UDiv: assert(!CI2->isNullValue() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); case Instruction::SDiv: assert(!CI2->isNullValue() && "Div by zero handled above"); if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); case Instruction::URem: assert(!CI2->isNullValue() && "Div by zero handled above"); return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); case Instruction::SRem: assert(!CI2->isNullValue() && "Div by zero handled above"); if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); case Instruction::And: return ConstantInt::get(CI1->getContext(), C1V & C2V); case Instruction::Or: return ConstantInt::get(CI1->getContext(), C1V | C2V); case Instruction::Xor: return ConstantInt::get(CI1->getContext(), C1V ^ C2V); case Instruction::Shl: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.shl(C2V)); return UndefValue::get(C1->getType()); // too big shift is undef case Instruction::LShr: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V)); return UndefValue::get(C1->getType()); // too big shift is undef case Instruction::AShr: if (C2V.ult(C1V.getBitWidth())) return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V)); return UndefValue::get(C1->getType()); // too big shift is undef } } switch (Opcode) { case Instruction::SDiv: case Instruction::UDiv: case Instruction::URem: case Instruction::SRem: case Instruction::LShr: case Instruction::AShr: case Instruction::Shl: if (CI1->equalsInt(0)) return C1; break; default: break; } } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { APFloat C1V = CFP1->getValueAPF(); APFloat C2V = CFP2->getValueAPF(); APFloat C3V = C1V; // copy for modification switch (Opcode) { default: break; case Instruction::FAdd: (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FSub: (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FMul: (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FDiv: (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); return ConstantFP::get(C1->getContext(), C3V); case Instruction::FRem: (void)C3V.mod(C2V); return ConstantFP::get(C1->getContext(), C3V); } } } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { // Perform elementwise folding. SmallVector<Constant*, 16> Result; Type *Ty = IntegerType::get(VTy->getContext(), 32); for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { Constant *LHS = ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); Constant *RHS = ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); } return ConstantVector::get(Result); } if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { // There are many possible foldings we could do here. We should probably // at least fold add of a pointer with an integer into the appropriate // getelementptr. This will improve alias analysis a bit. // Given ((a + b) + c), if (b + c) folds to something interesting, return // (a + (b + c)). if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) return ConstantExpr::get(Opcode, CE1->getOperand(0), T); } } else if (isa<ConstantExpr>(C2)) { // If C2 is a constant expr and C1 isn't, flop them around and fold the // other way if possible. if (Instruction::isCommutative(Opcode)) return ConstantFoldBinaryInstruction(Opcode, C2, C1); } // i1 can be simplified in many cases. if (C1->getType()->isIntegerTy(1)) { switch (Opcode) { case Instruction::Add: case Instruction::Sub: return ConstantExpr::getXor(C1, C2); case Instruction::Mul: return ConstantExpr::getAnd(C1, C2); case Instruction::Shl: case Instruction::LShr: case Instruction::AShr: // We can assume that C2 == 0. If it were one the result would be // undefined because the shift value is as large as the bitwidth. return C1; case Instruction::SDiv: case Instruction::UDiv: // We can assume that C2 == 1. If it were zero the result would be // undefined through division by zero. return C1; case Instruction::URem: case Instruction::SRem: // We can assume that C2 == 1. If it were zero the result would be // undefined through division by zero. return ConstantInt::getFalse(C1->getContext()); default: break; } } // We don't know how to fold this. return nullptr; } /// isZeroSizedType - This type is zero sized if its an array or structure of /// zero sized types. The only leaf zero sized type is an empty structure. static bool isMaybeZeroSizedType(Type *Ty) { if (StructType *STy = dyn_cast<StructType>(Ty)) { if (STy->isOpaque()) return true; // Can't say. // If all of elements have zero size, this does too. for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; return true; } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { return isMaybeZeroSizedType(ATy->getElementType()); } return false; } /// IdxCompare - Compare the two constants as though they were getelementptr /// indices. This allows coercion of the types to be the same thing. /// /// If the two constants are the "same" (after coercion), return 0. If the /// first is less than the second, return -1, if the second is less than the /// first, return 1. If the constants are not integral, return -2. /// static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) { if (C1 == C2) return 0; // Ok, we found a different index. If they are not ConstantInt, we can't do // anything with them. if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) return -2; // don't know! // We cannot compare the indices if they don't fit in an int64_t. if (cast<ConstantInt>(C1)->getValue().getActiveBits() > 64 || cast<ConstantInt>(C2)->getValue().getActiveBits() > 64) return -2; // don't know! // Ok, we have two differing integer indices. Sign extend them to be the same // type. int64_t C1Val = cast<ConstantInt>(C1)->getSExtValue(); int64_t C2Val = cast<ConstantInt>(C2)->getSExtValue(); if (C1Val == C2Val) return 0; // They are equal // If the type being indexed over is really just a zero sized type, there is // no pointer difference being made here. if (isMaybeZeroSizedType(ElTy)) return -2; // dunno. // If they are really different, now that they are the same type, then we // found a difference! if (C1Val < C2Val) return -1; else return 1; } /// evaluateFCmpRelation - This function determines if there is anything we can /// decide about the two constants provided. This doesn't need to handle simple /// things like ConstantFP comparisons, but should instead handle ConstantExprs. /// If we can determine that the two constants have a particular relation to /// each other, we should return the corresponding FCmpInst predicate, /// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in /// ConstantFoldCompareInstruction. /// /// To simplify this code we canonicalize the relation so that the first /// operand is always the most "complex" of the two. We consider ConstantFP /// to be the simplest, and ConstantExprs to be the most complex. static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { assert(V1->getType() == V2->getType() && "Cannot compare values of different types!"); // Handle degenerate case quickly if (V1 == V2) return FCmpInst::FCMP_OEQ; if (!isa<ConstantExpr>(V1)) { if (!isa<ConstantExpr>(V2)) { // Simple case, use the standard constant folder. ConstantInt *R = nullptr; R = dyn_cast<ConstantInt>( ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); if (R && !R->isZero()) return FCmpInst::FCMP_OEQ; R = dyn_cast<ConstantInt>( ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); if (R && !R->isZero()) return FCmpInst::FCMP_OLT; R = dyn_cast<ConstantInt>( ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); if (R && !R->isZero()) return FCmpInst::FCMP_OGT; // Nothing more we can do return FCmpInst::BAD_FCMP_PREDICATE; } // If the first operand is simple and second is ConstantExpr, swap operands. FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) return FCmpInst::getSwappedPredicate(SwappedRelation); } else { // Ok, the LHS is known to be a constantexpr. The RHS can be any of a // constantexpr or a simple constant. ConstantExpr *CE1 = cast<ConstantExpr>(V1); switch (CE1->getOpcode()) { case Instruction::FPTrunc: case Instruction::FPExt: case Instruction::UIToFP: case Instruction::SIToFP: // We might be able to do something with these but we don't right now. break; default: break; } } // There are MANY other foldings that we could perform here. They will // probably be added on demand, as they seem needed. return FCmpInst::BAD_FCMP_PREDICATE; } static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1, const GlobalValue *GV2) { auto isGlobalUnsafeForEquality = [](const GlobalValue *GV) { if (GV->hasExternalWeakLinkage() || GV->hasWeakAnyLinkage()) return true; if (const auto *GVar = dyn_cast<GlobalVariable>(GV)) { Type *Ty = GVar->getValueType(); // A global with opaque type might end up being zero sized. if (!Ty->isSized()) return true; // A global with an empty type might lie at the address of any other // global. if (Ty->isEmptyTy()) return true; } return false; }; // Don't try to decide equality of aliases. if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2)) if (!isGlobalUnsafeForEquality(GV1) && !isGlobalUnsafeForEquality(GV2)) return ICmpInst::ICMP_NE; return ICmpInst::BAD_ICMP_PREDICATE; } /// evaluateICmpRelation - This function determines if there is anything we can /// decide about the two constants provided. This doesn't need to handle simple /// things like integer comparisons, but should instead handle ConstantExprs /// and GlobalValues. If we can determine that the two constants have a /// particular relation to each other, we should return the corresponding ICmp /// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. /// /// To simplify this code we canonicalize the relation so that the first /// operand is always the most "complex" of the two. We consider simple /// constants (like ConstantInt) to be the simplest, followed by /// GlobalValues, followed by ConstantExpr's (the most complex). /// static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, bool isSigned) { assert(V1->getType() == V2->getType() && "Cannot compare different types of values!"); if (V1 == V2) return ICmpInst::ICMP_EQ; if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && !isa<BlockAddress>(V1)) { if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && !isa<BlockAddress>(V2)) { // We distilled this down to a simple case, use the standard constant // folder. ConstantInt *R = nullptr; ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); if (R && !R->isZero()) return pred; pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); if (R && !R->isZero()) return pred; pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); if (R && !R->isZero()) return pred; // If we couldn't figure it out, bail. return ICmpInst::BAD_ICMP_PREDICATE; } // If the first operand is simple, swap operands. ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1, isSigned); if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) return ICmpInst::getSwappedPredicate(SwappedRelation); } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { if (isa<ConstantExpr>(V2)) { // Swap as necessary. ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1, isSigned); if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) return ICmpInst::getSwappedPredicate(SwappedRelation); return ICmpInst::BAD_ICMP_PREDICATE; } // Now we know that the RHS is a GlobalValue, BlockAddress or simple // constant (which, since the types must match, means that it's a // ConstantPointerNull). if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { return areGlobalsPotentiallyEqual(GV, GV2); } else if (isa<BlockAddress>(V2)) { return ICmpInst::ICMP_NE; // Globals never equal labels. } else { assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); // GlobalVals can never be null unless they have external weak linkage. // We don't try to evaluate aliases here. if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) return ICmpInst::ICMP_NE; } } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { if (isa<ConstantExpr>(V2)) { // Swap as necessary. ICmpInst::Predicate SwappedRelation = evaluateICmpRelation(V2, V1, isSigned); if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) return ICmpInst::getSwappedPredicate(SwappedRelation); return ICmpInst::BAD_ICMP_PREDICATE; } // Now we know that the RHS is a GlobalValue, BlockAddress or simple // constant (which, since the types must match, means that it is a // ConstantPointerNull). if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { // Block address in another function can't equal this one, but block // addresses in the current function might be the same if blocks are // empty. if (BA2->getFunction() != BA->getFunction()) return ICmpInst::ICMP_NE; } else { // Block addresses aren't null, don't equal the address of globals. assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && "Canonicalization guarantee!"); return ICmpInst::ICMP_NE; } } else { // Ok, the LHS is known to be a constantexpr. The RHS can be any of a // constantexpr, a global, block address, or a simple constant. ConstantExpr *CE1 = cast<ConstantExpr>(V1); Constant *CE1Op0 = CE1->getOperand(0); switch (CE1->getOpcode()) { case Instruction::Trunc: case Instruction::FPTrunc: case Instruction::FPExt: case Instruction::FPToUI: case Instruction::FPToSI: break; // We can't evaluate floating point casts or truncations. case Instruction::UIToFP: case Instruction::SIToFP: case Instruction::BitCast: case Instruction::ZExt: case Instruction::SExt: // If the cast is not actually changing bits, and the second operand is a // null pointer, do the comparison with the pre-casted value. if (V2->isNullValue() && (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; if (CE1->getOpcode() == Instruction::SExt) isSigned = true; return evaluateICmpRelation(CE1Op0, Constant::getNullValue(CE1Op0->getType()), isSigned); } break; case Instruction::GetElementPtr: { GEPOperator *CE1GEP = cast<GEPOperator>(CE1); // Ok, since this is a getelementptr, we know that the constant has a // pointer type. Check the various cases. if (isa<ConstantPointerNull>(V2)) { // If we are comparing a GEP to a null pointer, check to see if the base // of the GEP equals the null pointer. if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { if (GV->hasExternalWeakLinkage()) // Weak linkage GVals could be zero or not. We're comparing that // to null pointer so its greater-or-equal return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; else // If its not weak linkage, the GVal must have a non-zero address // so the result is greater-than return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; } else if (isa<ConstantPointerNull>(CE1Op0)) { // If we are indexing from a null pointer, check to see if we have any // non-zero indices. for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) if (!CE1->getOperand(i)->isNullValue()) // Offsetting from null, must not be equal. return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; // Only zero indexes from null, must still be zero. return ICmpInst::ICMP_EQ; } // Otherwise, we can't really say if the first operand is null or not. } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { if (isa<ConstantPointerNull>(CE1Op0)) { if (GV2->hasExternalWeakLinkage()) // Weak linkage GVals could be zero or not. We're comparing it to // a null pointer, so its less-or-equal return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; else // If its not weak linkage, the GVal must have a non-zero address // so the result is less-than return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { if (GV == GV2) { // If this is a getelementptr of the same global, then it must be // different. Because the types must match, the getelementptr could // only have at most one index, and because we fold getelementptr's // with a single zero index, it must be nonzero. assert(CE1->getNumOperands() == 2 && !CE1->getOperand(1)->isNullValue() && "Surprising getelementptr!"); return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; } else { if (CE1GEP->hasAllZeroIndices()) return areGlobalsPotentiallyEqual(GV, GV2); return ICmpInst::BAD_ICMP_PREDICATE; } } } else { ConstantExpr *CE2 = cast<ConstantExpr>(V2); Constant *CE2Op0 = CE2->getOperand(0); // There are MANY other foldings that we could perform here. They will // probably be added on demand, as they seem needed. switch (CE2->getOpcode()) { default: break; case Instruction::GetElementPtr: // By far the most common case to handle is when the base pointers are // obviously to the same global. if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { // Don't know relative ordering, but check for inequality. if (CE1Op0 != CE2Op0) { GEPOperator *CE2GEP = cast<GEPOperator>(CE2); if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0), cast<GlobalValue>(CE2Op0)); return ICmpInst::BAD_ICMP_PREDICATE; } // Ok, we know that both getelementptr instructions are based on the // same global. From this, we can precisely determine the relative // ordering of the resultant pointers. unsigned i = 1; // The logic below assumes that the result of the comparison // can be determined by finding the first index that differs. // This doesn't work if there is over-indexing in any // subsequent indices, so check for that case first. if (!CE1->isGEPWithNoNotionalOverIndexing() || !CE2->isGEPWithNoNotionalOverIndexing()) return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. // Compare all of the operands the GEP's have in common. gep_type_iterator GTI = gep_type_begin(CE1); for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); ++i, ++GTI) switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), GTI.getIndexedType())) { case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; case -2: return ICmpInst::BAD_ICMP_PREDICATE; } // Ok, we ran out of things they have in common. If any leftovers // are non-zero then we have a difference, otherwise we are equal. for (; i < CE1->getNumOperands(); ++i) if (!CE1->getOperand(i)->isNullValue()) { if (isa<ConstantInt>(CE1->getOperand(i))) return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; else return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. } for (; i < CE2->getNumOperands(); ++i) if (!CE2->getOperand(i)->isNullValue()) { if (isa<ConstantInt>(CE2->getOperand(i))) return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; else return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. } return ICmpInst::ICMP_EQ; } } } } default: break; } } return ICmpInst::BAD_ICMP_PREDICATE; } Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, Constant *C1, Constant *C2) { Type *ResultTy; if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), VT->getNumElements()); else ResultTy = Type::getInt1Ty(C1->getContext()); // Fold FCMP_FALSE/FCMP_TRUE unconditionally. if (pred == FCmpInst::FCMP_FALSE) return Constant::getNullValue(ResultTy); if (pred == FCmpInst::FCMP_TRUE) return Constant::getAllOnesValue(ResultTy); // Handle some degenerate cases first if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { CmpInst::Predicate Predicate = CmpInst::Predicate(pred); bool isIntegerPredicate = ICmpInst::isIntPredicate(Predicate); // For EQ and NE, we can always pick a value for the undef to make the // predicate pass or fail, so we can return undef. // Also, if both operands are undef, we can return undef for int comparison. if (ICmpInst::isEquality(Predicate) || (isIntegerPredicate && C1 == C2)) return UndefValue::get(ResultTy); // Otherwise, for integer compare, pick the same value as the non-undef // operand, and fold it to true or false. if (isIntegerPredicate) return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(Predicate)); // Choosing NaN for the undef will always make unordered comparison succeed // and ordered comparison fails. return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate)); } // icmp eq/ne(null,GV) -> false/true if (C1->isNullValue()) { if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) // Don't try to evaluate aliases. External weak GV can be null. if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(C1->getContext()); } // icmp eq/ne(GV,null) -> false/true } else if (C2->isNullValue()) { if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) // Don't try to evaluate aliases. External weak GV can be null. if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(C1->getContext()); else if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(C1->getContext()); } } // If the comparison is a comparison between two i1's, simplify it. if (C1->getType()->isIntegerTy(1)) { switch(pred) { case ICmpInst::ICMP_EQ: if (isa<ConstantInt>(C2)) return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); case ICmpInst::ICMP_NE: return ConstantExpr::getXor(C1, C2); default: break; } } if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { APInt V1 = cast<ConstantInt>(C1)->getValue(); APInt V2 = cast<ConstantInt>(C2)->getValue(); switch (pred) { default: llvm_unreachable("Invalid ICmp Predicate"); case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); } } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); APFloat::cmpResult R = C1V.compare(C2V); switch (pred) { default: llvm_unreachable("Invalid FCmp Predicate"); case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); case FCmpInst::FCMP_UNO: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); case FCmpInst::FCMP_ORD: return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); case FCmpInst::FCMP_UEQ: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpEqual); case FCmpInst::FCMP_OEQ: return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); case FCmpInst::FCMP_UNE: return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); case FCmpInst::FCMP_ONE: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_ULT: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpLessThan); case FCmpInst::FCMP_OLT: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); case FCmpInst::FCMP_UGT: return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_OGT: return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); case FCmpInst::FCMP_ULE: return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); case FCmpInst::FCMP_OLE: return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || R==APFloat::cmpEqual); case FCmpInst::FCMP_UGE: return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); case FCmpInst::FCMP_OGE: return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || R==APFloat::cmpEqual); } } else if (C1->getType()->isVectorTy()) { // If we can constant fold the comparison of each element, constant fold // the whole vector comparison. SmallVector<Constant*, 4> ResElts; Type *Ty = IntegerType::get(C1->getContext(), 32); // Compare the elements, producing an i1 result or constant expr. for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){ Constant *C1E = ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); Constant *C2E = ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); } return ConstantVector::get(ResElts); } if (C1->getType()->isFloatingPointTy() && // Only call evaluateFCmpRelation if we have a constant expr to avoid // infinite recursive loop (isa<ConstantExpr>(C1) || isa<ConstantExpr>(C2))) { int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. switch (evaluateFCmpRelation(C1, C2)) { default: llvm_unreachable("Unknown relation!"); case FCmpInst::FCMP_UNO: case FCmpInst::FCMP_ORD: case FCmpInst::FCMP_UEQ: case FCmpInst::FCMP_UNE: case FCmpInst::FCMP_ULT: case FCmpInst::FCMP_UGT: case FCmpInst::FCMP_ULE: case FCmpInst::FCMP_UGE: case FCmpInst::FCMP_TRUE: case FCmpInst::FCMP_FALSE: case FCmpInst::BAD_FCMP_PREDICATE: break; // Couldn't determine anything about these constants. case FCmpInst::FCMP_OEQ: // We know that C1 == C2 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLT: // We know that C1 < C2 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); break; case FCmpInst::FCMP_OGT: // We know that C1 > C2 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); break; case FCmpInst::FCMP_OLE: // We know that C1 <= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) Result = 0; else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) Result = 1; break; case FCmpInst::FCMP_OGE: // We known that C1 >= C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) Result = 0; else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) Result = 1; break; case FCmpInst::FCMP_ONE: // We know that C1 != C2 // We can only partially decide this relation. if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) Result = 0; else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) Result = 1; break; } // If we evaluated the result, return it now. if (Result != -1) return ConstantInt::get(ResultTy, Result); } else { // Evaluate the relation between the two constants, per the predicate. int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned((CmpInst::Predicate)pred))) { default: llvm_unreachable("Unknown relational!"); case ICmpInst::BAD_ICMP_PREDICATE: break; // Couldn't determine anything about these constants. case ICmpInst::ICMP_EQ: // We know the constants are equal! // If we know the constants are equal, we can decide the result of this // computation precisely. Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); break; case ICmpInst::ICMP_ULT: switch (pred) { case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: Result = 1; break; case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: Result = 0; break; } break; case ICmpInst::ICMP_SLT: switch (pred) { case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: Result = 1; break; case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: Result = 0; break; } break; case ICmpInst::ICMP_UGT: switch (pred) { case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: Result = 1; break; case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: Result = 0; break; } break; case ICmpInst::ICMP_SGT: switch (pred) { case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: Result = 1; break; case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: Result = 0; break; } break; case ICmpInst::ICMP_ULE: if (pred == ICmpInst::ICMP_UGT) Result = 0; if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; break; case ICmpInst::ICMP_SLE: if (pred == ICmpInst::ICMP_SGT) Result = 0; if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; break; case ICmpInst::ICMP_UGE: if (pred == ICmpInst::ICMP_ULT) Result = 0; if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; break; case ICmpInst::ICMP_SGE: if (pred == ICmpInst::ICMP_SLT) Result = 0; if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; break; case ICmpInst::ICMP_NE: if (pred == ICmpInst::ICMP_EQ) Result = 0; if (pred == ICmpInst::ICMP_NE) Result = 1; break; } // If we evaluated the result, return it now. if (Result != -1) return ConstantInt::get(ResultTy, Result); // If the right hand side is a bitcast, try using its inverse to simplify // it by moving it to the left hand side. We can't do this if it would turn // a vector compare into a scalar compare or visa versa. if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { Constant *CE2Op0 = CE2->getOperand(0); if (CE2->getOpcode() == Instruction::BitCast && CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); return ConstantExpr::getICmp(pred, Inverse, CE2Op0); } } // If the left hand side is an extension, try eliminating it. if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned((ICmpInst::Predicate)pred)) || (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned((ICmpInst::Predicate)pred))){ Constant *CE1Op0 = CE1->getOperand(0); Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); if (CE1Inverse == CE1Op0) { // Check whether we can safely truncate the right hand side. Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); if (ConstantExpr::getCast(CE1->getOpcode(), C2Inverse, C2->getType()) == C2) return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); } } } if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || (C1->isNullValue() && !C2->isNullValue())) { // If C2 is a constant expr and C1 isn't, flip them around and fold the // other way if possible. // Also, if C1 is null and C2 isn't, flip them around. pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); return ConstantExpr::getICmp(pred, C2, C1); } } return nullptr; } /// isInBoundsIndices - Test whether the given sequence of *normalized* indices /// is "inbounds". template<typename IndexTy> static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { // No indices means nothing that could be out of bounds. if (Idxs.empty()) return true; // If the first index is zero, it's in bounds. if (cast<Constant>(Idxs[0])->isNullValue()) return true; // If the first index is one and all the rest are zero, it's in bounds, // by the one-past-the-end rule. if (!cast<ConstantInt>(Idxs[0])->isOne()) return false; for (unsigned i = 1, e = Idxs.size(); i != e; ++i) if (!cast<Constant>(Idxs[i])->isNullValue()) return false; return true; } /// \brief Test whether a given ConstantInt is in-range for a SequentialType. static bool isIndexInRangeOfSequentialType(SequentialType *STy, const ConstantInt *CI) { // And indices are valid when indexing along a pointer if (isa<PointerType>(STy)) return true; uint64_t NumElements = 0; // Determine the number of elements in our sequential type. if (auto *ATy = dyn_cast<ArrayType>(STy)) NumElements = ATy->getNumElements(); else if (auto *VTy = dyn_cast<VectorType>(STy)) NumElements = VTy->getNumElements(); assert((isa<ArrayType>(STy) || NumElements > 0) && "didn't expect non-array type to have zero elements!"); // We cannot bounds check the index if it doesn't fit in an int64_t. if (CI->getValue().getActiveBits() > 64) return false; // A negative index or an index past the end of our sequential type is // considered out-of-range. int64_t IndexVal = CI->getSExtValue(); if (IndexVal < 0 || (NumElements > 0 && (uint64_t)IndexVal >= NumElements)) return false; // Otherwise, it is in-range. return true; } template<typename IndexTy> static Constant *ConstantFoldGetElementPtrImpl(Type *PointeeTy, Constant *C, bool inBounds, ArrayRef<IndexTy> Idxs) { if (Idxs.empty()) return C; Constant *Idx0 = cast<Constant>(Idxs[0]); if ((Idxs.size() == 1 && Idx0->isNullValue())) return C; if (isa<UndefValue>(C)) { PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType()); Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs); assert(Ty && "Invalid indices for GEP!"); Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace()); if (VectorType *VT = dyn_cast<VectorType>(C->getType())) GEPTy = VectorType::get(GEPTy, VT->getNumElements()); return UndefValue::get(GEPTy); } if (C->isNullValue()) { bool isNull = true; for (unsigned i = 0, e = Idxs.size(); i != e; ++i) if (!cast<Constant>(Idxs[i])->isNullValue()) { isNull = false; break; } if (isNull) { PointerType *PtrTy = cast<PointerType>(C->getType()->getScalarType()); Type *Ty = GetElementPtrInst::getIndexedType(PointeeTy, Idxs); assert(Ty && "Invalid indices for GEP!"); Type *GEPTy = PointerType::get(Ty, PtrTy->getAddressSpace()); if (VectorType *VT = dyn_cast<VectorType>(C->getType())) GEPTy = VectorType::get(GEPTy, VT->getNumElements()); return Constant::getNullValue(GEPTy); } } if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { // Combine Indices - If the source pointer to this getelementptr instruction // is a getelementptr instruction, combine the indices of the two // getelementptr instructions into a single instruction. // if (CE->getOpcode() == Instruction::GetElementPtr) { Type *LastTy = nullptr; for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); I != E; ++I) LastTy = *I; // We cannot combine indices if doing so would take us outside of an // array or vector. Doing otherwise could trick us if we evaluated such a // GEP as part of a load. // // e.g. Consider if the original GEP was: // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, // i32 0, i32 0, i64 0) // // If we then tried to offset it by '8' to get to the third element, // an i8, we should *not* get: // i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, // i32 0, i32 0, i64 8) // // This GEP tries to index array element '8 which runs out-of-bounds. // Subsequent evaluation would get confused and produce erroneous results. // // The following prohibits such a GEP from being formed by checking to see // if the index is in-range with respect to an array or vector. bool PerformFold = false; if (Idx0->isNullValue()) PerformFold = true; else if (SequentialType *STy = dyn_cast_or_null<SequentialType>(LastTy)) if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx0)) PerformFold = isIndexInRangeOfSequentialType(STy, CI); if (PerformFold) { SmallVector<Value*, 16> NewIndices; NewIndices.reserve(Idxs.size() + CE->getNumOperands()); NewIndices.append(CE->op_begin() + 1, CE->op_end() - 1); // Add the last index of the source with the first index of the new GEP. // Make sure to handle the case when they are actually different types. Constant *Combined = CE->getOperand(CE->getNumOperands()-1); // Otherwise it must be an array. if (!Idx0->isNullValue()) { Type *IdxTy = Combined->getType(); if (IdxTy != Idx0->getType()) { unsigned CommonExtendedWidth = std::max(IdxTy->getIntegerBitWidth(), Idx0->getType()->getIntegerBitWidth()); CommonExtendedWidth = std::max(CommonExtendedWidth, 64U); Type *CommonTy = Type::getIntNTy(IdxTy->getContext(), CommonExtendedWidth); Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, CommonTy); Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, CommonTy); Combined = ConstantExpr::get(Instruction::Add, C1, C2); } else { Combined = ConstantExpr::get(Instruction::Add, Idx0, Combined); } } NewIndices.push_back(Combined); NewIndices.append(Idxs.begin() + 1, Idxs.end()); return ConstantExpr::getGetElementPtr( cast<GEPOperator>(CE)->getSourceElementType(), CE->getOperand(0), NewIndices, inBounds && cast<GEPOperator>(CE)->isInBounds()); } } // Attempt to fold casts to the same type away. For example, folding: // // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), // i64 0, i64 0) // into: // // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) // // Don't fold if the cast is changing address spaces. if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { PointerType *SrcPtrTy = dyn_cast<PointerType>(CE->getOperand(0)->getType()); PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType()); if (SrcPtrTy && DstPtrTy) { ArrayType *SrcArrayTy = dyn_cast<ArrayType>(SrcPtrTy->getElementType()); ArrayType *DstArrayTy = dyn_cast<ArrayType>(DstPtrTy->getElementType()); if (SrcArrayTy && DstArrayTy && SrcArrayTy->getElementType() == DstArrayTy->getElementType() && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace()) return ConstantExpr::getGetElementPtr( SrcArrayTy, (Constant *)CE->getOperand(0), Idxs, inBounds); } } } // Check to see if any array indices are not within the corresponding // notional array or vector bounds. If so, try to determine if they can be // factored out into preceding dimensions. SmallVector<Constant *, 8> NewIdxs; Type *Ty = PointeeTy; Type *Prev = C->getType(); bool Unknown = !isa<ConstantInt>(Idxs[0]); for (unsigned i = 1, e = Idxs.size(); i != e; Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { if (isa<ArrayType>(Ty) || isa<VectorType>(Ty)) if (CI->getSExtValue() > 0 && !isIndexInRangeOfSequentialType(cast<SequentialType>(Ty), CI)) { if (isa<SequentialType>(Prev)) { // It's out of range, but we can factor it into the prior // dimension. NewIdxs.resize(Idxs.size()); uint64_t NumElements = 0; if (auto *ATy = dyn_cast<ArrayType>(Ty)) NumElements = ATy->getNumElements(); else NumElements = cast<VectorType>(Ty)->getNumElements(); ConstantInt *Factor = ConstantInt::get(CI->getType(), NumElements); NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); Constant *PrevIdx = cast<Constant>(Idxs[i-1]); Constant *Div = ConstantExpr::getSDiv(CI, Factor); unsigned CommonExtendedWidth = std::max(PrevIdx->getType()->getIntegerBitWidth(), Div->getType()->getIntegerBitWidth()); CommonExtendedWidth = std::max(CommonExtendedWidth, 64U); // Before adding, extend both operands to i64 to avoid // overflow trouble. if (!PrevIdx->getType()->isIntegerTy(CommonExtendedWidth)) PrevIdx = ConstantExpr::getSExt( PrevIdx, Type::getIntNTy(Div->getContext(), CommonExtendedWidth)); if (!Div->getType()->isIntegerTy(CommonExtendedWidth)) Div = ConstantExpr::getSExt( Div, Type::getIntNTy(Div->getContext(), CommonExtendedWidth)); NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); } else { // It's out of range, but the prior dimension is a struct // so we can't do anything about it. Unknown = true; } } } else { // We don't know if it's in range or not. Unknown = true; } } // If we did any factoring, start over with the adjusted indices. if (!NewIdxs.empty()) { for (unsigned i = 0, e = Idxs.size(); i != e; ++i) if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); return ConstantExpr::getGetElementPtr(PointeeTy, C, NewIdxs, inBounds); } // If all indices are known integers and normalized, we can do a simple // check for the "inbounds" property. if (!Unknown && !inBounds) if (auto *GV = dyn_cast<GlobalVariable>(C)) if (!GV->hasExternalWeakLinkage() && isInBoundsIndices(Idxs)) return ConstantExpr::getInBoundsGetElementPtr(PointeeTy, C, Idxs); return nullptr; } Constant *llvm::ConstantFoldGetElementPtr(Type *Ty, Constant *C, bool inBounds, ArrayRef<Constant *> Idxs) { return ConstantFoldGetElementPtrImpl(Ty, C, inBounds, Idxs); } Constant *llvm::ConstantFoldGetElementPtr(Type *Ty, Constant *C, bool inBounds, ArrayRef<Value *> Idxs) { return ConstantFoldGetElementPtrImpl(Ty, C, inBounds, Idxs); }